흰쥐를 대상으로 벤지딘 노출에 의해 형성된 혈장 단백질 부가체의 생물학적모니터링 적용과 에탄올과 phenobarbital이 미치는 영향

김치년,이세훈,노재훈 大韓産業醫學會 2002 대한직업환경의학회지 Vol.14 No.4

목 적 : 에탄올 또는 phenobarbital를 섭취한 근로자들이 벤지딘 및 벤지딘계 염료에 노출되는 경우 혈장 단백질 부가체를 이용한 생물학적 노출평가가 정확하게 이루어지도록 흰쥐를 대상으로 대사에 영향을 주는 물질로 알려진 에탄올과 phenobarbital이 벤지딘 투여시 혈장 단백질 부가체 형성에 미치는 영향을 파악하고 N-acetulation에 미치는 영향도 함께 평가하였다. 방 법 : 실험 대상인 흰쥐를 대조군, 에탄올 전처치군, phenobarbital 전처치군으로 분류하여 벤지딘을 투여하기 24시간 전에 에탄올과 phenobarbital을 전처치하였다. 혈액시료 채취는 투여전과 투여후 30분, 3, 6, 9, 12, 24, 48, 72, 96, 144시간에서 각 군을 대상으로 5마리를 대상으로 실시하였다. 채취한 혈액은 즉시 혈장을 분리하고 부가체를 염기 가수분해하여 방향족 아민의 형태로 전환시켰다. 가수분해한 벤지딘, 모노아세틸벤지딘 그리고 4-아미노비페닐을 유도체화 과정 없이 역상 액체크로마토그래프를 이용하여 분리하였으며, 그 물질들은 선택성과 감도가 높은 전기화학검출기로 정량분석하였다. 분석한 대사산물은 혈장 단백질 결합지수와 N-acetylation 비로 표현하였다. 결 과 : 에탄올 또는 phenobarbital 전처치군의 벤지딘-혈장 단백질 결합지수. 모노아세틸벤지딘-혈장 단백질 결합지수, 4아미노비페닐-혈장 단백질 결합지수가 대조군보다 높아 에탄올 또는 phenobarbital이 혈장 단백질의 부가체 형성을 증가시키는 역할을 하였다. 혈장 단백질 부가체에서 일어나는 N-acetylation은 전처치에 상관없이 모든 군에서 유사하게 나타났으며 헤모글로빈 부가체의 경우와난 다르게 N-acetylation이 적게 이루어졌다. 헤모글로빈 부가체에서는 4-nitroso-4'-N-acetylbiphenyl이 가장 많이 형성되었지만 혈장 단백질에는 다른 양상이었으며 에탄올이 방향족 아민류와 함께 노출이 되면 N-acetylation이 증가한다는 효과도 적었다. 또한 1회 경구 투여 후에 형성된 혈장 단백질 부가체는 전처치헤모글로빈 부가체보다 빠르게 증가하고 감소하는 경향이 있었다. 결 론 : 에탄올과 phenobarbital은 벤지딘 투여에 의해 형성되는 혈장 단백질 부가체를 증가시켰다. 그러나 헤모글로빈 부가체와는 다르게 N-acetylation을 증가하는 경향은 없었다. 혈장단백질 부가체는 벤지딘 노출에 대한 누적효과가 헤모글로빈 구가체보다 상대적으로 적었다. 따라서 벤지딘 노출근로자들은 대상으로 혈장 단백질 부가체를 생물학적 모니터링으로 이용할 때는 에탄올이나 phenobatbital에 대한 영향을 고려하는 것이 필요하면 최근에 대한 노출평가에만 활용되는 것이 바람직하다. Objectives : The effects of ethanol and phenobarbital, which are known to affect metabolism of xenobiotics, on the formation of benzidine- and its metabolites-plasma protein adducts in rats administered benzidine were evaluated. Methods : The experimental rats were divided into the control, ethanol and phenobarbital groups. The experimental groups (ethanol and phenobarbital group) were pretreated with ethanol (1g/㎏) or phenobarbital (80㎎/㎏) 24 hours prior to the oral administration of benzidine (0.5mmol/㎏). Blood samples were obtained from the vena cava from 5 rats in each group; and at 30 min, 3 h, 6 h, 9 h, 12 h, 24 h, 48 h, 72 h, 96 h, and 144 after the administration of benzidine using heparin treated syringes. The plasma protein levels were separated immediately atfer taking blood samples. The adducts were underwent basic hydrolysis to convert them into aromatic amines. The hydroluzed benzidine, monoacetulbenzidine, and 4-aminobiphenyl were analyzed by reverse-phased liquid chromatography with an electrochemical detector. The quantitative amount of the matabolites waw expressed by the plasma protein binding index(PBI). Results : similar to the hemoglobin adducts, the levels of the plasma protein adducts of the ethanol and phenobarbital groups (benzidine-, monoacetylbenzidine-, and 4-amino-biphenyl-PBI) were higher than those of the control group. These results are attributable to the fact that ethanol and phenobarbital induced to the plasma protein adduct formation. The N-acetylation ratio in the control group was highest at 72 h with 2.34. In the ethanol group, it was highest at 72 h with a ratio of 2.46 and was highest in the phenobabital group at 72 h with a ratio of 2.43. The N-acetulation ratio of the plasma protein adducts was relatively lower than that of the hemoglobin adducts. The level of the plasma protein adduct increased more rapidluy than the hemoglobin adducts in all experimental gruops regadless of the pretreatment, and decreased rapidluy after reaching the maxi-mum level. Conclusion : The above results indicate that ethanol and phenobarbital increased the level of plasma protein adduct formation. The plasma protein adducts tended to decrease more rapidly than the hemoglobin adducts in the body after benzidine exposure. This results in this study result suggests that the effects of ethanol or phenobarbital need to be considered in the biochemical monitoring, and that the level of the plasma protein adducts be a more proper biomaker than the hemoglobin adducts for assessing the short term exposure to a benzidine and benxidine based dye.

염화비닐 노출 근로자의 시료채취시기에 따른 요중 thiodiglycolic acid의 농도 변화

김현수,김치년,원종욱,차봉석,이경종,노재훈 大韓産業醫學會 2006 대한직업환경의학회지 Vol.18 No.2

목적: 본 연구는 염화비닐 및 폴리염화비닐수지 제조공장의 VCM 노출 근로자들을 대상으로 소변 시료채취 시기에 따른 요중 TDGA 농도의 변화를 알아보고자 하였다. 방법: VCM 및 PVC 제조공장 남성 근로자 31명을 대상으로 공기중 VCM 개인노출평가를 실시하였으며 소변내 TDGA 배설 양상을 알아보기 위해 3일 휴식 후 척 작업 시작 전(TDGA1), 1일 작업종료 후(TDGA2), 1일 작업 한 다음날 작업 전(TDGA3) 소변을 채취하였다. VCM에 노출되지 않은 대조군 30명에 대해 작업종료 후 소변을 채취하였다. 공기 중 VCM의 측정 및 본석은 NIOSH 공정시험법 No. 1007에 따라 실시하였다. 요중 TDGA 분석을 위하여 소변을 trimethylsilyldiazomethane(2.0 M in diethyl ether)으로 메틸화 반응하여 가스크로마트그래피/펄스불꽃광도검출기로 분석하였다. 결과: VCM 노출 후 요중 TDGA가 배설되어 감소하는 시기를 조사하기위해 대조군과 VCM 노출 근로자들의 3일 휴식 후 작업 시작 전 요중 TDGA 농도 (TDGA1)를 비교한 결과 각각 0.179±0.271 mg/g creatinine, 0.218±0.443 mg/g creatinine으로 통계학적으로 유의한 차이가 없었다. 1일 작업 종료 후 요중 TDGA 농도(TDGA2)는 0.434±0.623 mg/g creatinine, 1일 작업 한 다음날 작업전 요중 TDGA 농도(TDGA3)는 0.767±1.056 mg/g creatinine으로 순차적으로 증가하였다. 하루 노출량을 평가하기 위해 공기 중 VCM 농도와 요중 TDGA와의 단순회귀분석 결과 1일 작업한 다음날 작업 전 요중 TDGA 농도(TDGA3)와 공기 중 VCM 농도와의 관련성은 R^(2)=0.4215로 1일 작업종료 후 요중 TDGA 농도(TDGA2)보다 높았다. 결론: VCM 노출 후 3일이 경과하면 대조군의 요중 TDGA 농도 수준으로 감소하여 요중 TDGA의 배설 반감기가 3일 이내인 것으로 판단된다. 또한, 하루 근무하고 그 다음날 작업 전에 채취한 요중 TDGA 농도(TDGA3)가 전날 근무시의 VCM노출량과 상관성이 가장 높아 하루 동안의 VCM노출을 평가하기 위한 유용한 생물학적 지표로 사용할 수 있을 것으로 판단된다. Objectives: The study was performed to investigate the changes of urinary thiodiglycolic acid (TDGA) concentration in workers exposed to vinyl chloride monomer (VCM) according to the time of sampling urine. Methods: The personal exposure to airborne VCM was assessed and urinary TDGA concentration was sampled in 31 workers employed in a VCM and polyvinyl chloride (PVC) manufacturing factory. Urinary TDGA was sampled three times: before the start of the shift after 3 days off (TDGA 1), after the end of the first-day shift (TDGA2) and before starting the following day shift after completing the one- day shift (TDGA3). Urinary TDGA in 30 workers who had not been exposed to airborne VCM was sam- pled after the end of the shift. A gas chromatography/pulsed flame photometric detector (GC/PFPD) was utilized to analyze TDGA concentration in urine after the urine was methylated with trimethylsilyldia- zomethane (2.0M in diethyl ether). Results: The creatinine level was 0.179±0.271 mg/g in the control workers and 0.218±0.443 mg/g in the workers before the start of the shift after 3 days off (TDGA1), showing no significant difference (p=0.7035). Urine samples were compared according to sampling time in order to investigate the change of urinary TDGA concentration in the case of continuous exposure to airborne VCM. In VCM-exposed workers, urinary creatinine concentration was 0.434±0.623 mg/g in TDGA2 and 0.767±1.056 mg/g in TDGA3, which indicated a gradual but significant increase (p=0.024). In terms of the statistical correlation between airborne VCM and urinary TDGA to evaluate exposure dose per day, of the three urinary TDGA concentrations, TDGA3, showed the highest degree of regression (R^(2)=0.4215) with 8h-TWA airborne VCM concentration. Conclusion: Based on this result, the excretion half-life of urinary TDGA was assumed to be less than 3 days, because the concentration of urinary TDGA at 3 days after exposure to airborne VCM was decreased to the level of urinary TDGA concentration in the control workers. The concentration of urinary TDGA increased in the case of continuous shift, due to the accumulation of residual metabolites of TDGA. It was considered that TDGA3 can be applied as a useful biological index to evaluate the exposure dose of airborne VCM during one day because TDGA3 showed the highest correlation with the exposure dose of airborne VCM in the previous shift day.

3단 및 변형 2단 카세트 샘플러의 공기중 수산화나트륨 포집효율의 실험적 연구

윤영식,김치년,김현수,노재훈 한국산업위생학회 2002 한국산업보건학회지 Vol.12 No.1

Sodium hydroxide(NaOH) is one of the chemicals produced great quantity in Korea. It variously uses for acid neutralization, petroleum refining, electroplating, metal cleaning, laundering, bleaching, washing dish, manufacture of paper, etc. NaOH is used in various field of industry but information on the sampling efficiency for NaOH IS seldom provided. The objective of this study was to compare the sampling efficiency of the three-piece cassette sampler with the modified two-piece cassette sampler. The three-pieces cassette consisted of an inlet cover, a spacer, a mixed cellulose ester membrane(MCE) filter, a back-up pad and a bottom. The modified two-pieces cassette consisted of the same parts as a three-piece cassette without a spacer. The whole inner surface of the 2-piece cassette was loaded with MCE filter to ensure that all of the aspirated NaOH. The air sampling of airborne NaOH WAS performed according to the Occupational Safety and Health Administration(OSHA) analytical method manual ID-121 that is used for the method of occupational environment measurement and analysis. Air samplings were per-formed by simultaneous samplings using the three-piece and modified two-piece cassette sampler at the same time and same place in the chemical plants. The significant difference between average adsorbed amounts on the MCE filters of the three-piece and modified two-piece cassette sampler was found. Sampling amounts of the modified two-piece cassette sampler was 1.84 times higher than that of the three-piece casstte sampler(p<0.01). An average 47% of NaOH was collected on the upper (inlet+middle-rim) side of the modified two-piece cassette. As the result of his study, it is verified that the modified two-piece cassette sampler is more effective than the three-piece cassette sampler for collection of airborne NaOH.

흰쥐에 정맥 주사한 수용성 크롬의 분포 및 배설

김용래,김치년,노재훈 한국산업위생학회 2001 한국산업보건학회지 Vol.11 No.1

Chromium exposure can be in the forms of environmental pollution and occupational exposure. The harmful effects of chromium on the body greatly differ depending on its valence or solubility. Accordingly, the recommended permissible exposure limit for each chromium compound is different. This study investigated the increase or decrease of distribution and excretion of total chromium exposed simultaneously the soluble Cr+6 and Cr+3 compounds. There were no difference of total chromium concentration in plasma, red bloods cells, urine, organs between simul-taneously injected and individually injected soluble Cr+6 and Cr+3 compounds. The chromium clearances in urine also showed that there were two phases in the two groups. In the first phase, biological half lives of the total chromium of the two groups have been similar within 24hr., but in the second phase, biological half life of the group injected simultane-ously was 62.7 hr. and was less than that of the other group's 188.3 hr. The average concentration of total chro- mium in plasma was same with the control, and that of RBCs was 0.218 n ㏖/㎖ and was slightly increased in comparison with 0.121 n ㏖/㎖ of the control, which was not statistically significant. As a result, there were no differences of distribution and excretion of chromium between the group exposed sim-ultaneously and the other group exposed separately the soluble Cr+6 and Cr+3 compounds. The biological half life of chromium of the former group in urine was less than that of the other group.

전처리방법에 따른 산화에틸렌 분석법의 평가

이신영,김치년,조영봉,오상용,노재훈 한국산업위생학회 2003 한국산업보건학회지 Vol.13 No.2

The limit of detection(LOD), pooled coefficient of variation(pooled CV), desorption dffciency(DE), and stability after desorption by pre-treatments was compared and evaluated for analyzing the Ethylene oxide(EO) sampling on HBr-coated Charcoal tube, The results were as follows: 1. The EO's LOD was 2,483ug/sample when using the desorptin solvent, benzene : CS2(99:1), and 1.919ug/sample after using DMF. The result of the sample that passed DMF desorption and was derivativized was 1.301ug/sample. 2. EO's pooled CV was 0.00503 when using the solvent benzene:CS(99:1), after desorption with DMF, the result was 0.00329, and the result of those derivativized by DMF desorption was 0.00514. 3. EO's DE using the solvent benzene:CS(99:1) was 92.13%, atter desorption with DMF, it was 102.75%, and the result of those studied after being derivativized by DMF desorption was 96.47%. 4. EO's stability for the sample with the solvent benzene:CS(99:1), comparing result of next-day analysis to same-day was 96.81% after desorption was 95.69% These results were in accordance with the less than 5% given by OSHA methoc 50. In conclusion, when pre-treatment of the EO in the HBr=coated charcoal, analyzing immediately after desorption by DMF is more simple, precise, and efficient than other analyzing methods, and the stabiity of the sample 24 hours after desorption was alst established.

공기 중 toluene diisocyanate의 포집방법에 따른 요중 toluene diamine의 관련성

박근철,김치년,김현수,김형렬,노재훈 한국산업위생학회 2003 한국산업보건학회지 Vol.13 No.1

Toluene diisocyanate(TDI) has been known the materials which is induced occupational asthma, is mostly used by the materials of industrial polyurethane, excreted as toluene diamine(TDA) in case of occurring metabolism in the human body when it inhaled. This research is demonstrated to make scrutiny into efficiency of two differentways of sampling in comparison with the cocentration after make use of the open cassette holder and the modified 2-piece cassette holder which are originaly existing to doing sampling 2,4-TDI as 2,6 TDI in the air, and to present more adequate way to TDI sampling in the air and to present more adequate way to TDI sampling in the air from comparing concentration TDA in a worker's urine with concentration of TDI which is being sampling each ways And this study want to grasp the influence for TDA excretion by exposing TDI from the general character of workers. The study was experimented on the 22 workers from the factory where is pperated paining work using by paints from poly urethane. This study was performed to identify the personal character of workers by using the questionnaire. analysed TDI from 44 sample each in the middle of morning and afternoon and TDA from the 17 workers by take their urine. Open cassette holder is manufactured to face the filter with the outside by remove the modified 2-piece cassette holder eliminated he middle of section and top of the upper holder. As a result of analysis, the concentration of TDI in the air is higher on the mokigied 2-piece cassette holder than the open cassette holder for sampling, There was no different on the concentration of urinary TDA by personal character. The concentration of TDI in the air had a relation with the concentration of urinary TDA no matter what kind of sampling method used, but the sampling by modified 2-piece cassette holder had more relation than sampling by open face cassette holder. As a result of this experiment, the concentration of TDI by sampling from the each cassette holder has shown to us significant relation with the concentration of urinary TDA.

흰쥐에 있어서 Ethanol과 Phenobarbital이 트리클로로에틸렌 대사에 미치는 영향

이경종,노재훈,김치년,조명화,차봉석,문영한 大韓産業醫學會 1993 대한직업환경의학회지 Vol.5 No.1

Trichloroethylene is widely used for organic solvent in many industries. There are many workers who are exposed to trichloroethylene in Korea. If workers are exposed to trichloroethylene after ingestion of ethanol or phenobarbital, there might be an increased risk of toxicity due to combined exposures of chemicals. This study was performed to find out the influences of ethanol and phenobarbital on the levels of trichloroethylene in rats. Trichloroethylene was administered orally at the doses of 150, 750, 1,500, and 3,000mg/kg after pretreatment of 4g/kg ethanol or 80mg/kg phenobarbital. Trichloroethylene in blood was not detected at 12 hours after oral administration of trichloroethylene. Administered amount of trichloroethylene and its total blood concentration had a positive relationship. The level of blood trichloroethylene was decreased faster in ethanol and phenobarbital pretreated groups than in the control group. Amounts of urinary free trichloroethanol were larger at the doses of 150, 750, and 1,500mg/kg of trichloroethylene with pretreated phenobarbital group than in the control group. Total amounts of urinary conjugated trichloroethanol were larger in pretreated ethanol and phenobarbital groups than in the control group. In the phenobarbital pretreated group, there was a increasing tendency of excertion of urinary trichloroacetic acid. These results showed that intake of ethanol and phenobarbital may alter the metabolism of trichloroethylene in rats.

톨루엔 디이소시아네이트 폭로 근로자들의 생물학적 모니터링

안연순,노재훈,김치년,박윤정,정상혁 大韓産業醫學會 1995 대한직업환경의학회지 Vol.7 No.2

Toluene diisocyanate(TDI) is widely used in the production of flexible polyurethane foams, as well as in the formulation of polyurethane paints and coatings. The commercial material is generally a mixture of 2,4- and 2, 6-TDI, the predominant mix being 80% 2,4 and 20% 2,6-TDI. The 2,4-isomer is considerably more reactive than the 2,6-TDI at ambient temperatures due to steric factors involving the positions of the isocyanate groups relative to the ring methyl group. Because of this difference in the reactivities of the isomers, it seemed probable that there might be an increase in the amount of 2,6-TDI offgased relative to the 2,4-isomer. Therefore a relative enrichment of the 2,6-TDI has been found in industrial atmospheres. Toluene diamines, which are metabolites of TDI, in urine have a linear relation with exposure to TDI, so that urianry TDA could be used as a biological index of the exposure to TDI. This study was conducted to investigate the distribution of TDI isomer in industrial atmospheres and to propose proper biological monitoring methods by identifying the relationships between the environmental TDI exposure and concentration of TDA in urine. Concentrations of 2, 4-TDI and 2, 6-TDI in air were 4.38㎍/㎥ and 25.43㎍/㎥, respectively. The Threshold Limited Value of 40㎍/㎥ was exceeded for the 2, 6-TDI in about 46.8%(22 samples) of the samples, while the 2, 4-TDI was not at all exceeded. The ratio between 2, 4-TDI and 2, 6-TDI varied in air samples in the range of 2.4%:97.6%-51.0%:49.0%. There was an enrichment of 2, 6-TDI in air relative to the 2, 4-TDI. Concentrations of 2, 4-TDA and 2, 6-TDA in urine were 1.31㎍/g creatinine and 4.16㎍/g creatinine, respectively. The ratio between 2, 4-TDA and 2, 6-TDA varied in urine samples in the range of 1.4%:98.6%-99.9%:0.1%. There was an enrichment of 2, 6-TDA in urine relative to the 2, 4-TDA. No relation between the concerations of TDA isomer in urine and concerations of TDI isomer in air was found. Above results of this study, workers were more exposed to the 2, 6-TDI relative to the 2, 4-TDI in industrial atmospheres. Therefore, the establishment of TLV for 2, 6-TDI should be considered. Also, the further studies on biological monitorigs of workers exposed to TDI should be continued.

벤지딘계 염료제조 사업장 근로자의 벤지딘 폭로

노재훈,안연순,김규상,김치년,김현수 大韓産業醫學會 1995 대한직업환경의학회지 Vol.7 No.2

To evaluate the differences of benzidine exposure patterns of the workers in two benzidine-based dye manufacturing factories, the concentration of benzidine in air, blood and urine were measured. The air levels of benzidine dihydrochloride and benzidine-based dye were measured by high performance liquid chromatography with ultraviolet detector. Blood samples were collected at 3 hours after exposure and urine samples were collected at the end of shift. Blood and urine samples were analyzed by high performance liquid chromatography with electrochemical detector. The level of benzidine in reaction process (input, diazotization, and coupling) was 0.381±7950g/㎥. The blood benzidine was deteced in 25 workers among 38 in reaction process and their mean levels were 0.0153±.0376 ng/mg Hb. The urinary benzidine was detected for 11 workers among 38 workers in the reaction process. The level of benzidine-based dye in drying and packing process was 52.1748±14.4111g/㎥. The blood benzidine was deteced in 6 workers among 38 in drying and packing process and their mean levels was 0.0062±.0274 ng/mg Hb. The urinary benzidine was detected for 1 worker among 38 workers exposed to benzidine-based dye. The blood and urinary benzidine were detected in workers exposed to benzidine-based dye. Such results suggested that some part of benzidine-based dye was metaboized to benzidine. Therefore, some regulations for manufacturing and use of the benzidine-based dye are needed to prevent its hazards in industries.

인천지역 TDI 노출 작업자에서 직업성천식 유병율

김형렬,김철우,홍윤철,전형준,김치년,김현수,이지나,신주연,고동희,노재훈 大韓産業醫學會 2004 대한직업환경의학회지 Vol.16 No.2

목적 : TDI는 직업성천식을 일으키는 대표적인 물질로 알려져 있다. 과거 TDI에 노출된 작업자들의 천식 발생률을 5~6%가량 보고하였고, 국내에서도 2-20%에 이르는 유병율을 보고한바 있다. 작업환경이 많이 개선되고, 노출량이 감소된 최근에도 TDI에 의한 직업성천식에 대한 보고가 많이 이루어지고 있어, 이에 대한 적극적인 조사와 진단과정을 통해 유병율을 구하고 질병발생의 변화양상을 파악해 보고자 하였다. 방법 : 인천지역에서 특수건강진단을 수행하는 2개 기관의 TDI 노출 근로자 400여명 중, 사업장의 규모가 50인 이상이며 사업주가 연구진행을 허락한 사업장에서 근무하는 근로자 중 직접적으로 TDI에 노출되는 작업에 종사하는 근로자 170명을 연구대상으로 하였다. 이들에 대해 설문지와 산업의학의사의 면담을 통한 작업관련성 평가를 근거로 정밀대상자를 선정하고 이들에 대해 메타콜린 유발시험, TDI 유발시험 등을 수행하여 직업성천식을 확인하였다. 결과 : 설문조사 결과 11명이 직업과 관련하여 천식증상을 보이는 것으로 나타났고(6.9%), 이중 7명에서 메타콜린 유발검사 양성소견을 보였다. TDI에 의한 특이유발시험 결과 1명에서 양성반응이 나타나, 이 집단에서 TDI에 의한 직업성천식의 유병율은 0.58%였다. 결론 : 과거 국내연구에서 TDI에 의한 직업성천식의 유병율이 2~20%에 이르렀던 데 비해, 본 연구에서는 0.58%로 나타났다. 이는 국외 논문에서도 나타나는 경향으로 작업장 노출량 감소로 점차 발생률이 감소하는 양상을 보이고 있다. 그러나 이미 증상이 나타난 근로자들이 부서를 옮기거나, 직장을 그만둠으로 인해 그 유병율이 과소평가되었을 가능성도 있다고 판단된다. Objecdives: This study was carried out to estimate the prevalence of isocyanate-induced occupational asthma in toluene diisocyanate (TDI) exposed workers. Methods: We examined 170 workers who had been directly exposed to TDI through a medical questionnaire, physical examination, and pulmonary function test. Based on screening examination, workers with suspected occupational asthma were selected for further evaluation such as methacholine and TDI challenge tests. Results: Eleven (6.9%) among 170 workers complained of symptoms of occupational asthma. and 7 among these 11 symptomatic workers showed positive responses to the methacholine challenge test (4.1 %). One spray painter was confirmed as having the TDI induced occupational asthma following a positive response to TDI challenge test. Conclusions: The prevalence of TDI-induced asthma was at 0.58% was lower than that for former studies (2-20%). Improved workplace environment, lower level of TDI exposure compared to the past, and the healthy workers effect may have contributed to this low rate of asthma prevalence in workers with TDI exposure.